Hydraulic classifier employing vertical and vortical currents



E. L. WIEGAND HYDRAULIC CLASSIFIER EMPLOYING VERTICAL AND VORTICAL CURRENTS Filed Dec. 16, 1944 4 Sheets-Sheet l A TTORNE f5 HYDRAULIC CLASSIFIER EMFLOYING VERTICAL AND VORTICAL CURRENTS Filed Dec. 16, 1944 j '1; 1 94. E. L. WIEGAND 4 Sheets-Sheet 2 m L w. W 5

HYDRAULIC CLASSIFIER EMPLOYING VERTICAL AND VORTICAL CURRENTS Filed D66. 16, 1944 June 1, 1948. E. WIEGAND 4 Sheets-Sheet 3 flaw/1v. L. Wat/m0 INVENTOR June 9' E. L. WIEGAND 2,52

HYDRAULIC CL-ASSIFIIJR EMPLOYING VERTICAL AND VORTICAL CURRENTS Filed Dec. 16, 1944 4 Sheets-Sheet 4 Patented June 1, 1948 HYDRAULIC CLASSIFIER EMPLOYING VER- TICAL AND VORTICAL CURRENTS Edwin L. Wiegand, Rye, N. Y., assignor to Orefraction Incorporated, Pittsburgh, Pa., a corporation of Pennsylvania Application December 16, 1944, Serial No. 568,459

7 Claims. (01. 209-159) My invention relates to the classification of material particles by hydraulic means, and the prin cipal object of my invention is to provide new and improved classification, particularly of a precision character, and new and improved apparatus for carrying out such classifications.

In the drawings accompanying this specification, and forming a part of this application, I have shown, for purposes of illustration, an embodiment of apparatus which my invention may assume, and in these drawings:

Figure 1 is a side elevation ofthis illustrative form of apparatus,

Figure 2 is a fragmentary, enlarged view, of an upper portion of the apparatus shown in Figure 1, a portion being in longitudinal cross-section,

Figure 3 is-a fragmentary, enlarged view, of a lower portion of the apparatus shown in Figure 1,

Figure 4 is a longitudinal cross-section, on an enlarged scale, of a sorting column forming part of the apparatus shown in Figure 1, and

Figure 5 is a cross-section taken on the line 5-5 of Figure 4, looking in the direction of the arrows.

Referring more particularly to Figures 1 and 2, the apparatus comprises settling chamber means S which includes a downwardly tapering conical chamber ||l having an opening connected to a sorting column l2 which may be fed with water,

or other suitable liquid, by means of a water jacket |3.

The particles to be separated or classified are fed, in a desirably wetted condition, usuall in the form of a slurry, to the settling chamber means S through a funnel l4, here shown as communicating with a plurality of pipes I5 the lower open ends l6 of which terminate well below the per end of the chamber means.

By reason of the water fed to the jacket l3, the particles fed to the chamber means S are subjected to hydraulic counter-current settling. The particles which succeed in descending through the lwdraulic counter-current and are discharged fromthe lower end of the apparatus, I term underage, and the particles which are carried upwardly by the counter-current and are discharged from the upper end of the apparatus, I term overage. As will appear more fully hereinafter, the apparatus is so constructed and arranged that, if desired, two separate and distinct overage products may be obtained simultaneously, or one or the other of different overag -products.

"At the upper marg n of the conical chamber I0 is here shown a cylindrical portion I'I, soldered or otherwise suitably fastened, water-tight to the conical chamber 0. Slidable up and down on the cylindrical portion I is a cylindrical ring l8, preferably provided on its inner periphery with a packing member |9 so that the ring I8 will form a water-tight joint with the cylindrical portion I! in any adjusted position of the ring.

Dependent upon the position of the ring l8, overage is adapted to be discharged over the upper margin 20 of the ring into a launder 2|. The launder 2| comprises an inner wall 22 which fits the outer surface of the ring I8 and is soldered or otherwise suitably fastened, water-tight, to said outer surface. Th launder 2| further comprises an outer wall 23, of larger diameter and spaced concentricall from the inner wall 22, the upper margin 24 of the outer wall 23 being disposed above the upper margin 20 of the ring I 8. The lower margins of the outer wall 23 and inner wall 22 are suitably joined, water-tight, to a bottom wall 25 which defines an inclined plane. The launder 2| has a discharge spout 26 at its lowest level, through which overage which has flowed into the launder may be discharged.

this means being here shown as three threaded rods 21, apart. Each rod 21 has a flattened part 28 here shown as soldered or otherwise suitably fastened to the outer wall 23 of the launder 2|. The threaded. rods 21 pass freely through apertures in support means 29; and knurled nuts 30, cooperating with the threaded rods, are provided respectively to move and hold the rods in adjusted position. The support means 29 is here shown as extending laterally from a standard 3| to which it is suitably fastened.

My invention contemplates whirling of the liquid in the conical chamber Ill and its upward extension comprising the cylindrical portion l1 and the ring Hi, to produce a vortex therein. This may be accomplished in various ways one 01 which is shown in the drawings. In the construction illustrated rotatable vanes 32' are provided. Any suitable number of vanes 32 may be used, four being used in the present instance. Each vane 32 is pivotally mounted on a pivot 33 adjustably carried by a stem 34, as will more fully appear, a nut 35 being provided, for cooperation with threads on the outer end of thepivot 33, to fasten the respective vane 32 in adjusted rotative position about the pivot 33. Each stem 34 is adjustably carried by a sleeve 36, as will more fully appear, the sleeve 36 being adjustable slidably on a rod 31. Each rod 31 is here shown as extending downwardly at a slight angle, so that adjustmeat of a sleeve 88 on the respective rod will adjust the respective vane 82 in a direction generally transverse to the wall of the conical chamber l0. Thus a vane 82 may be positioned as shown in full lines or in the dotted lines 324:, or in any intermediate position, and also in the position shown in dotted lines 82b.

Each primary rod 81 base. vertically upwardly extending portion 88 having a reduced stud 38 extending through a hole in a rotatable wheel 48. The studs 88 are threaded at their ends and cooperate with nuts 4| which serve to hold the primary rods 81 fastened to the wheel 48, and also to hold a sheave 42 to the wheel, the sheave 42 having apertures through which the studs 39 pass. The sheave 42 has a groove 43 adapted to receive a belt 44 which also passes around a sheave 45 carried by the shaft of an electric motor 48 suitably carried by the standard 3|. Speed control means (not shown), of any suitable typ is preferably provided for the motor The wheel 48 has a journaled hub 41, fitting rotatably about a stationary bearing stud 48. The bearing stud 48 has a reduced lower end 48 about which fits a thrust bearing ring 58 engaged by the lower end of the hub 41 and held in place by a set screw 8| bearing against the reduced end 49,.

The upper end of thebearing stud 48 is enlarged and is suitably carried by the support means 29. The enlarged end of the bearing stud 48 has formed therein the funnel l4, and, extending downwardly from the funnel, a recess 52 with which communicate three downwardly extending passages 53. In the lower end of each passage 53 is fitted and suitably fastened a pipe nipple 54 adapted to be inserted freely into the respective upper end of one of the tubes l5, whereby the assembly comprising the bearing stud 48 and associated parts may be readily disassembled from the remainder of the apparatus, leaving the tubes l undisturbed.

The upper ends of the tubes I5 are desirably Desirably the taper of the conical wall 58 is approximately the same as that of the chamber l0, so that the normal distance between the wall 58 and the inside surface of the chamber i8 is approximately the same at any level.

The lower end of the auxiliary conical wall 58 is here shown as closed, water-tight, by a disc 51; and as providedwith a suitable number of dis charge spouts 88, in this instance four. Each spout 58 passes through an aperture 59 in the wall of the conical chamber l8 into the space provided by a second launder 88. Each discharge spout 58 is soldered or otherwise fastened, watertight, to the margin of the respective aperture 59 in which it is disposed. The second launder 88 is here shown as having a wall 6| soldered, at its upper margin, to the outside of the conical chamber I0 and having an inclined bottom 82 leading to a discharge spout 83. v

The auxiliary conical wall 58 is here shown as having an upward cylindrical extension 64. Telescopically cooperable with the extension 84 is a cylindrical wall part 85 unitary with an upwardly and inwardly tapering wall part 86. The conical wall part 68 terminates in a circular aperture the margin 6-! of which is here shown as below the upper margin of the cylindrical portion I! of the settling chamber. .It' will be evident that the construction just described provides central discharge wall means for receiving overage, as will more fully appear.

The cylindrical wall part 85 while slidable up and down in the cylindrical extension 84 is frictionally held in the desired adjusted position. It will, of course, be evident that the amount of possible up and down adjustment of the cylindrical wall part 65 in the cylindrical extension 84, and hence the adjustment of the margin 81, will depend upon the length of the cylindrical parts 64, 65 and this length can be made any desired, suitable amount.

The opening ii in the lower end of the conical chamber it! has its margin connected, watertight, to a relatively short length of pipe ea. As can be seen in Figure 4, the lower end of the pipe 88 fits in, and is connected, water-tight, in an aperture in a flange 88, the flange 69 having a lateral extension 18 suitably supported by the standard 3|. Thus the flange 88 supports the settling chamber means S, and to further support and steady it, a ring 1| having a lateral extension 12 suitably supported by the standard 3 I is provided.

The flange 69 supports and is connected, watertight, to a second flange 13, by bolts and nuts 14 (Figure 2). Within the pipe 11 are disposed a plurality of. tubes 19, desirably thin-walled. The tubes 18 are of sufllcient number so as to fit snugly in'cont'act with each other in the pipe 11 when pushed thereinto. This produces longitudinally extending passages within the pipe 11, of honey-comb effect. When the tubes 18 have been pushed into the pipe 11, they are sweated or tinned together in place, leaving free passages through the tubes and any interstitial spaces.

The tubes 19 extend vertically downward in the pipe 11 from about the level of the upper side of the flange 18 to a level just above a row 88 of circumferentially spaced holes 8| extending transversely through the pipe 11. Below the row of holes are additional rows of holes at successively lower levels, in this instance two rows 88a, 80b the holes in which are of the same size 4 as in row 80, the holes in the successive rows being desirably staggered, circumferentially. In addition, there is a lowermost row 82 of circumferential spaced holes 83, there being a greater number of holes in the row 82 than in the other rows, and the holes 83 being smaller than the holes 8| in the other rows. The provision of a lowermost row of holes such as the row 82, prevents clogging or bridging of the underage that might occur across the lower part of the pipe 11.

The water jacket I3 is here shown as comprising a cylindrical outer wall 84 integral with an annular upper end wall 85, the end wall 85 having an aperture 88 fitting around the pipe I1 and, soldered or otherwise suitably fastened, waterj tight, to the pipe 11. The end wall 85 is here shown as disposed at a level substantially above the lower ends of the tubes 18, thefcylindrical wall 84 extending downwardly to a level substantially above the row 82 of holes 83, and the'water jacket being closed at its bottom by a conical wall 81' soldered or otherwise suitably fastened. watertight. to the lower end of the cylindrical wall 88, and to the pipe 11 at a level below the row 82 of holes 83.

The outer wall 84 has an internally threaded nipple 88 through which water may be admitted to the water jacket l3, from a threaded pipe 89 cooperating with the nipple.

In order to provide a. desirably uniform feed of water to the rows 88, 88a, 88b, 82 of holes. the upper, end wall 85 has an auxiliary cylindrical baiile wall 98 depending therefrom, the auxiliary wall 98 being of smaller diameter than the outer wall 84 and extending downwardly to a level leaving a desired short gap 9| (here shown of uniform width) between the lower end of the auxiliary wall 98 and the conical bottom wall 81, whereby water'must flow through this gap to reach the hereinbeforementioned rows of holes.

Referring to Figure 1, water is fed to the pipe 89 through a valve 92 which is desirably graduated. so that the amount of flow of water into the water jacket I3 may be adjusted to an amount indicated by a pointer 92a.

Here shown as interposed in the pipe 89 is a T connection 93, the stem 94 of which has connected thereto a pipe 95 in turn connected to a pulsating means 96, diagrammatically shown. The pulsating means comprises a. casing 91 closed by a diaphragm 98. The diaphragm 98 is adapted to be vibrated by any suitable means, here diagrammatically shown as a crank disc 99 connected to the diaphragm by a connecting rod I88. The pulsating means may be used, if desired, to produce pulsations in the upwardly flowing hydraulic counter-current in the sorting colunm I2 and the settling chamber means S. This promotes teetering, and separation of the particles.

The discharge of underage is controlled by a control means I8l connected at the top to a Y pipe-fitting I82 having a branch I83 connected to an elbow I84 in turn connected to the lower end of the pipe 11. The upper end of the trunk I85 of the fitting I82 is closed by a member I86 through which a threaded rod I81 is disposed, water-tight but rotatable, for a purpose which will appear.

Underage is adapted to flow from the pipe 11, through an elbow I84 and Y fitting I82 into a pipe I88 (see Figure 3), and thence into a movable tank or sump I89. The sump I89 is connected to a bellows II8, desirably metallic, the bellows being fastened at its lower end air and watertight to a cover III, for the sump I89 and similarly fastened at its upper end to a. flange II2 suitably fastened to the lower end of the trunk I85 of the Y fitting I82. The pipe I88 extends freely through the bellows I|8 leaving an air space therebetween. Guide rods II3, held by nuts II4 to the flange II2, are provided for guiding the cover III, andthese rods have spaced adjustable nuts I I5 at their lower ends for limiting up and down movement of the cover III, and hence of the sump I89, to a desired amount.

The lower end of the sump is provided with a member IIG, which may be guided by suitable guide means H1. The member IIB has screwed thereinto or otherwise disposed therein a member II 6a, and which has an upwardly flaring conical bore II8, providing at its upper end a valve seat II9 for a conical valve body I28 fastened to the rod I81. The valve body I28 is relatively stationary but its position may be adjusted by turning a knurled head I28 on the rod I81. The member II8c is here shown as having a cylindrical bore I Ila extending downwardly from the conical bore I I8 and from the lower end of the cylindricalbore II8c underage is dischargeable either directly into a suitable receptacle I2I or into the bore of a spud or nozzle I I812 which may be screwed onto the lower end of the member II6a. The spud 8b has a downwardly tapering conical bore I I8b. Another spud I I50 is here shown as screwed onto the lower end of the spud I Itb, the spud I I8c having a downwardly tapering conical bore II8c forming a continuation of the bore II8b. By the provision of a plurality of spuds, the size of the ultimate discharge openin for underage may be changed to one not much larger than the maximum flow of underage encountered.

It will be evident that if the sump I89 moves downwardly, the valve opening, between the valve seat H9 and the valve body I28, will be increased, and if it moves upwardly, the valve opening will be reduced. The tendency of the sump I89 to move downwardly is balanced by an adjustable weight I22 on one end of a beam I23 the other end of the beam bearing a knife edge I24 cooperating with a knife edge bearing I25 carried by the cover plate III. The beam I23 has a fulcrum I25 (suitably supported 'by the standard 3|) having a suitably rounded surface I21, so that if the weight of undischarged underage in the sump I89 increases and the sump moves downwardly, the moment arm from the weight I22 to the point of engagement of the beam I23 with the fulcrum surface I21 will be increased, and if the weight of undischarged underage is decreased and the sump moves upwardly, said moment arm will be decreased. This prevents hunting, and insures that a satisfactory body of undischarged underage will be in the sump I89. The control means I8I and various other combinations and applications thereof are described and claimed in my copending application Serial Number 391,531,'now Patent No. 2,369,878, granted February 20, 1945. It will be evident that the control means I8I provides for continuous discharge of underage from the opening H8, at a rate controlled by the weight of undischarged underage. in the sump I89, the latter depending on the rate of production of underage. It also will be evident that the control means I8I serves to maintain steady hydrodynamic conditions in the sorting column I2 and the settling chamber means 8. This is important both in connection with the upward current in the sorting column and the upwardly progressing vortex current in the settling chamber means S.

The pipe I88 (Figure 3) is here shown as extending downwardly to a level well below the cover I I I, so that when the liquid level or underage level rises to the lower end of the pipe I88, air will'be trapped in the sump between this level and the level of the cover and, of course,. also in the space between the pipe I88 and the inside of the bellows I I8.

Referring now to the illustrated means for supporting and adjusting the vanes 32, the pivot 33 is in the form of a laterally projecting stud on a block I35 disposed at the side of the vane 32 opposite from the nut 35. The block has a hole I36 in which the stem 34 fits slidably. To hold the block I35 in any desired adjusted position on the stem 34 a set screw I31, extending in.- to the block I35, is provided. At its other end the stem 34 fits slidably in a hole I38 in a boss I39 projecting laterally from the sleeve 36. A set screw 8, extending into the boss I39, is provided for holding the stem in any desired adjusted position in the hole in the boss. The sleeve 36 may be held in any desired adjusted position on the rod 31 by one or more set screws Ill. While the same stem 34 may be used for any of the positions of the vane 32, a shorter stem may be used when the vane is adjusted to a position such as 32b, in the event that it is preferred that the lower end of the stem shall not extend into the liquid below the lower margin of the vane.

Thus the vanes 32 may be set so as to be near the surface of the liquid, generally horizontal or corresponding to the general angle of the surface of the liquid, or they may be set so as to be at any desired depth and position below the surface of the liquid, depending on the type of material being treated.

.The operation of the apparatus is as follows. It may be assumed that water is being fed to the water jacket l3 through the graduated valve 92 at a selected rate and that particles to be classified are being fed into the funnel l4, and that the vanes 32 are set in a desired position and are being rotated at a selected speed. It is of course apparent that the speed of the vanes and the rate of water feed may be separately adjusted to give the best combination for classifying a given feed of particles. When the body of liquid is caused to rotate by the vanes 32, the outer peripheral portion will rise in level and the inner peripheral portion will sink in level, so that the surface of the liquid is of downwardly dished form. It may be further assumed that the speed of rotation, and the position of the margin 20 of the ring l8 have been so selected that overage will flow over the margin 20 only, and no overage will flow over the margin 61, the latter being, under assumed conditions, higher than the level of the inner periphery of the surface of the liquid.

Some of the particles discharged from the openings [6 will descend in the conical chamber l and reach the sorting column i2, and these particles will be here subjected to hindered settling, especially in and just above the tubes 19, where the so-called teeter zone exists. Particles having a higher settling rate (the underage) fall through the teeter zone into the elbow I04 and thence into the sump I09 from which they are discharged in the manner hereinbefore described. The particles of lower settling rate (the overage) are carried upwardly by the hydraulic counter-current and discharged, under the assumed conditions, over the margin 20 of the ring l8 into the launder 24 and thence from the spout 25. It will be understood by those skilled in the art that the settling rate of particles is a function of several factors, including specific gravity and also size and shape and surface condition.

By rotation of the vanes 32 the resultant vortex provides a preliminary separation of the heavier from the lighter material inasmuch as the heavier material will tend to work relatively outwardly in the vortex and thence downwardly to the sorting column l2. On the other hand, the

lighter material will tend to work relatively inwardly in the vortex and progress upwardly with the rotating body of liquid until it is discharged over the margin 20. This increases the accuracy of the separation in the sorting column. It will, furthermore, be noted that the stream lines of water flow in the sorting column l2 must be vertically upward, for the most accurate results, and that the provision of the tubes 18 insures such vertical upward flow. This construction is of value even if the apparatus is used without a vortex rotation in the chamber II), but is of special value in combination with such vortex rotation because this rotation cannot produce rotation of the liquid and material in the sortin colurnn l2.

Another mode of operation of the apparatus, which i especially advantageous, is to adjust the position of the ring is and the position of the central discharge wall means 6' so that with a given speed of rotation of the vanes 32, and a given rate of water feed to the jacket it, no overage will be discharged over the margin 20, all the overage being discharged substantially radially inwardly over the margin 61 of the central discharge wall means. As hereinbefore pointed out the heavier material works relatively outwardly and downwardly in the vortex, and hence the lighter material, which works relatively toward the center of the vortex, is directly discharged over the margin 61 of the central discharge wall means and from there into the inside of the auxiliary conical wall 56 thence through the tubes 58 into the launder 60 and out of the .spout 63.

Still another especially advantageous mode of operation of the apparatus is to so adjust the poition of the ring l'8, and the position of the central discharge wall means 66 that, with a given speed of rotation of the vanes 32, and a given rate of water feed to the jacket l3, overage will be discharged outwardly over the margin 20 of the ring l8 into the launder 2|, and other overage will be discharged inwardly over the margin 61 of the central discharge wall means. Thus the apparatus will produce three different products: underage, and two kinds of overage. Speaking in relative terms, the underage will contain the larger, heavy particles, the overage discharged over the margin 20 of the ring [8 will contain the larger, lighter particles, and intermediate heavier particles, and the overage discharged over the margin 6'! of the central discharge wall means will contain the intermediate light and only the very smallest heavy particles.

The present apparatus enables the hydraulic classification of particles of fine mesh size, for example, 200 or 300 mesh to 400 mesh or finer, though it is not restricted to that purpose. The more complex minerals, for example, require finer grinding to release the values, but when ground to a sufficient fineness for that purpose, prior means of classifying the resultant particles are too ineihcient. The present apparatus is not only of great efficacy in classifying finely ground materials, but, in general, it gives very accurate classification, upon a gravity basis with only a reasonably close pre-sizing. It is also capable of quite accurately classifying and sub-classifying by size, relatively fine particles of material of the same specific gravity.

From the foregoing it will be apparent to those skilled in the art that the illustrated embodiment of the invention provides new and improved apparatus for classifying material particles and accordingly, accomplishes the principal object of the invention. 0n the other hand, it also will be obvious to those skilled in the art that the illustrated embodiment of the invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of the invention, or sacrificing all of the advantages thereof, and that accordingly,

, 9 I the disclosure herein is illustrative only, and th invention is not limited thereto.

I claim:

1. Apparatus for classifying material particles, comprising: hydraulic settling chamber means having outlet means for discharging underage and outlet means for discharging overage; means, including a vane, constructed and arranged to cause rotation of liquid in said chamber means; and means supporting said vane so constructed and arranged that said vane is bodily approximately vertically adjustable to selected positions, said supporting means comprising an approximately vertical rod, a block slidably adjustable on said rod, and means for fastening said vane to said block.

2. Apparatus for classifying material particles,

comprising: hydraulic settling chamber means I having outlet means for discharging underage and outlet means for discharging overage; means, including a vane, constructed and arranged to cause rotation of liquid in said chamber means; and means supporting said vane so constructed and arranged that said vane is bodily approximately horizontally adjustable to selected positions, said supporting means comprising an approximately horizontal first rod, a block slidably adjustable on said first rod, a second rod, means so constructed and arranged that said second rod is supported at an angle to said first rod, and means for holding said vane on said second rod.

3. Apparatus for classifying material particles, comprising: hydraulic settling chamber means having outlet means for discharging underage and outlet means for discharging overage; means,

including a vane, constructed and arranged to cause rotation of liquid in said chamber means; and. means supporting said vane so constructed and arranged that said vane is bodily approximately horizontally adjustable to selected positions, and vertically adjustable to selected positions, and rotatably adjustable to selected positions in a plane at an angle to the path of rotation of said vane, said supporting means comprising an approximately horizontal first rod, a first block slidably adjustable on 'said first rod, a second rod, means so constructed and arranged that said second rod is supported by said first block at an angle thereto and slidably adjustable with respect thereto, a second block slidably adjustable on said second rod, a pivot for said vane projecting laterally from said second block, and means for holding said vane to said second block in a selected rotative position about said pivot.

4. Apparatus for classifying material particles, comprising: hydraulic settling chamber means of circular section having outlet means for discharge of underage, and having an uppermost, circular peripheral margin; means for feeding liquid to said chamber means, so constructed and arranged that particles fed to said chamber means are subjected to hydraulic counter-current settlin overage receiving means, having a circular entrance opening co-axial with and disposed within said chamber means, so constructed and arranged that overage may flow inwardly over the margin of said opening; means, including an elongated vane, constructed and arranged to cause rotation of the liquid in the upper portion of said chamber means, about the vertical axis of said chamber means; and means, adjustably supporting said vane, so constructed and arranged that said vane may be positioned approximately horizontally at the general level of said margins and may be positioned approximately vertically at a lower level,

10 between said overage receiving means and said chamber means.

5. Apparatus for multiple classification of material particles, comprising hydraulic chamber means formed to receive classifying liquid and particles to be classified, including means to effect hydraulic counter-current settling in a lower portion thereof, and provided with an underage exit for the settling particles and with an inner over- 1 age exit and an outer overage exit, said outer overage exit being disposed substantially higher than said inner overage exit, and means constructed and arranged to swirl the overage from said counter-current separation in an upper portion of said chamber means to cause particles of said overage more susceptible to centrifugal action to move to and discharge at said higher overage exit, while particles less susceptible to said action move to and discharge at said lower inner overage exit.

6. Apparatus for multiple classification of material particles, comprising hydraulic chamber means formed to receive classifying liquid and particles to be classified, including means to efiect hydraulic counter-current settling in a lower portion thereof, and provided with an underage exit for the settling particles and with an inner overage exit and an outer overage exit, said outer overage exit being disposed substantially higher than said inner overage exit, and at least one of said overage exits being adjustable to vary the difierence in height between said overage exits, and means constructed and arranged to swirl the overage from said counter-current separation in an upper portion of said chamber means to cause particles of said overage' more susceptible to centrifugal action to' move to and discharge at said higher overage exit, while particles less susceptible to said action move to and discharge at said lower inner overage exit.

7. The process of effecting multiple classification of material particles which comprises subjecting the mineral particles to a hydraulic counter-current separation, removing settled particles, effecting upward movement of the liquid and particles rising from the counter-current separation, swirling said liquid and particles at a speed to cause a segregation of said particles on the basis of centrifugal action, and removing particles less susceptible to such action at a. relatively inward location and particles more susceptible to such action at a substantially higher relatively outward location.

EDWIN L. WIEGA REFERENCES CITED The following references are of record in the file of this patent:

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